Thermostat and method of making the same



Aug. 24 1926.

J. G. GOODHUE THERIOSTAT AND METHOD OF MAKING THE SAIE Filed March 14, 1923 Patented Aug. 24, 1926.

UNITED STATES PATENT OFFICE.

TULIA G. GOODHUEV, or EVANSTON, ILLINOIS, ASSIGNOR To THE TRUSTEES or THE ELECTRO THERMOS ATIC CONTROL COMPANY, or CHICAGO, ILLINOIS, a TRUST ESTATE.

THEBMOSTAT AND METHOD OF MAKING THE SAME...

Application filed March 14. 1923. Serial No. 624.877.

My invention relates to improvements in thermostatsand the method of making the same, and is particularly concerned with, though not limited to, improvements in thermostats for controlling electrical. circuits.

The objects of my invention are:

First: To provide a thermostat in which the expansion of one fluid having a large co-eflicient of expansion controls the position of the conducting fluid so as to close an electrical circuit, the thermostat being so constructed as to eliminate any influence on the movementvof the conducting fluid and the accuracy of the thermostat due to air or other'gases contained in the thermostat.

Second: To provide a thermostatsuch as described in which the fluid for actuating the circuit closing means is of such character as to respond to minute changes in temperature.

Third: To provide a thermostat of the character described in which the fluids referred to are of such character as to expedite the exhaustion of air and gases from the thermostat.

Fourth: To rovide a thermostat such as described whic is simple in construction, economical to manufacture and reliable; and

Fifth: To provide a novel method of constructing a thermostat of thecharacter described above.

Other objects of my invention Wlll ap-' pear as this descri tion progresses, reference being had to t e accompanying drawings, inwhich- Figure 1 is a central longitudinal section through one embodiment of my invention;

Figure 2 is a view illustrating the method of filling my improved thermostat;

Figure 3 is a side elevation illustrating a modified form of my invention; and

Figure 4 is a longitudinal section through a ortion of another embodiment thereof.

hroughout the several views similar reference characters will be used for referring to similar parts. I

The thermostat which I have illustrated in Figure l as embodying the features of my invention comprises an elongated tubular receptacle 5, which is preferably made of glass, but may be made of other suitable materials, and the tube 6 which passes through one of the end walls of the receptacle 5 and extends to a point adjacent the center of this receptacle. The outer end of this tube is provided with a spherically shaped expansion chamber 7, which in turn terminates in a nib 8 resulting from the sealing of the tube. Between the expansion chamber 7 and the receptacle 5, the tube 6 has a bulbous or spherically shaped projection 9, which communicates with the bore of the tube and in which is sealed the electrode 10 which forms one terminal of the circuit which is to be closed by the thermostat. A similar electrode 11 is sealed in the lower end or wall of the receptacle 5. This electrode forms the other terminal or con tact of the circuit to be closed.

In making my improved thermostat, the

tube with its expansion chamber and spherical projection 9 are sealed into one end of the receptacle 5, as shown in Figure 1. At this time the nib 8 is in the form of an open tube through which the fluid contents of the receptacle are to be passed. This is preferably accomplished by the use of two pieces of apparatus similar to the one shown in Figure 2. This apparatus comprises a receptacle 14 for holding one of the fluids to be injected into the receptacle 5. A tube 15 is secured to the bottom of the receptacle 14 and projects upwardly therefrom. The lower end of this tube opens through the bottom of the receptacle 14 and into a trap chamber 16 which is provided with a drain cock 17. A tube 18, projecting from the upper end of the trap chamber 16, may be connected with a source of suction by a flexible tube 19, or in any other suitable man ner. In filling the'thermostat with the desired fluids, the upper end of the tube 15 is inserted in the open tube or. nib 8 and the thermostat is lowered onto this tube until the lower end is submerged in the oil in the receptacle 14. The air in the receptacle will then be exhausted through the tube 15, the trap chamber 16 and the tube 19, whereupon atmospheric pressure pressing upon' the upper surface of the oil in the receptacle 14 will cause the oil to rise through the expansion chamber and the tube 6 and overflow into the receptacle 5. This may be continued untila predetermined quantity of oil has been admitted into the receptacle 5,

whereupon the suction upon the tube 15 is relieved and the thermostat removed from the tube 15. It is then lowered over the corresponding tube 15 and another receptacle 14 containing mercury. Upon the reestablishment of the suction through the secend tube 15, the mercury will be forced to rise into the receptacle 5 and completely fill it. In this operation, a slight amount of li uid may be carried over the top of the tu e 15 and down into the trap chamber 16 along with the air. It will collect in the bottoinof the trap chamber and can be removed therefrom through the stop cock 17 and returned to its receptacle. The thermostat, which is now substantially completely filled with mercury and oil, can be removed from the tube 15 turned right side up and placed in a bath maintained at the temperature at which the circuit is to be clo'ed through the electrodes. lVhen the fluid contents of the thermostat have acquired the temperature of the bath, mercury is removed from the expansion chamber and the tube until the mercury in the tube just contacts with the mercury in the spherical projection. The open nib or tube 8 is then connected with an air pump, which should be of such character as to create a 7 high vacuum in the expansion chamber and the upper portion of the tube. After this expansion has been completed, nitrogen or some other inert gas is admitted to the expansion chamber and the upper portion of the tube to dilute whatever air may be present therein and the tube or nib 8 is then again connected with the air pump and as much as possible of the mixed gases is removed from the expansion chamber at the upper end of the tube 6.

Thetube or nib 8 is then sealed and the entire thermostat inverted, thereby causing the mercury to descend into and entirely fill the expansion chamber of the tube 6, as well as the spherical projection 9. This causes any remaining gases present in the expansion tube to be displaced therefrom and crowdedup into the tube 6. In order to prevent any of these gases from lodging in the tube 6 and subsequently returning to the expansion chamber, I beat the expansion chamber to a temperature suificient to cause the mercury therein to expand and force any trapped air out of the tube 6 into the receptacle, where it collects adjacent the at this time upper end of the receptacle.

The thermostat is then a ain inverted, whereupon any gas containe in the receptacle Wlll rise to the space between the walls of the tube 6 and the upper end of thereceptacle, where it will be trap ed and prevented from returning to the expansion chamber and the tube. It will, of course, be understood that the space 13 indicated as being filled with this gas is very considerably exaggerated.

By first admitting the oil to the receptacle 5 and then admitting the mercury there to, I insure the complete removal of any trace of oil from the expansion chamber and the tube 6, because the mercury in rising through the expansion chamber and the tube 6 to the receptacle 5 will push any oil contained therein ahead of it into the receptacle 5. As the mercury flows into the receptacle 5 it will, of course, displace the oil contained therein upwardly so that when the receptacle is finally filled with mercury and oil, the mercury will at that time be in what is then the bottom of the receptacle 5, and the oil will be at the top thereof, but if the position of the thermostat is carefully changed,that is, if it is inverted-the oil will go to the top thereof without contami nating the interior of the tube.

I prefer to use olive oil for filling the space above the mercury in the receptacle 5, because olive oil has a high boiling point and will not boil under the low pressure existing in the completed thermostat at the temperature which causes the gas to be disengaged from the mercury and the oil nor at any temperature within the working range of the thermostat. Olive oil also has, as compared with mercury, a large co-efiicient of expansion and contraction, so that for a given change in temperature the column of mercury moves further than would be the case if the expansion of the mercury alone were depended upon for controlling the closing of the circuit between the two electrodes.

In the operation of my improved thermostat any condition which increases the temperature of the contents of the receptacle 5 will cause both the mercury and the olive oil to expand, thereby forcing a column of mercury up through the tube 6, and if the temperature reaches a redetermined point, the upper end of the co umn of mercury will make contact with the mercury trapped in the spherical projection 9 and thereby close the circuit between the two electrodes. If, subsequently, the conditions are such as to cause the contents of the receptacle 5 to become cooler, both the mercury and the oil will contact, thereby permitting the column of mercury to drop in the tube 6 and thus break the circuit between the two electrodes. As stated above, the high co-eflicint of expansion and contraction of olive oil causes a comparatively large movement of the mercury column upon a slight variation in temperature, so that my thermostat is extremely sensitive to changes in tem rature.

Another advantage resu ting from the elimination of theremaining gases from the expansion chamber is that there is no tendency for the mercury to oxidize or combine with any other element when the thread of mercury connecting the two electrodes is broken. If the potential between the two electrodes is comparatively high, there will ingelements, the mercury will be unaffected by this arcing.

It should also be noted that the construction of my thermostat described above is such that it is impossible for the oil to enter the tube 6. This is advantageous because the oil might combine in small quantities with the mercury at the point where the arcing takes place, so that in time the mercury would become fouled to the extent that it would have to be replaced.

In the modified form of my invention shown in Figure 3, I have provided the tube with a plurality of the spherical projections 9, each of which is provided with an electrode 10, so that the thermostat can be used for controlling a plurality of circuits which are respectively opened and closed at different predetermined temperatures.

\Vhile I the projections 9, such projections are not essential to the successfu functioning of my thermostat, and in Figure 4 I have shown the elctrodes 10 passing through the wall of the tube 6 and extending directly into the bore of this tube.

\Vhile I have described the details of construction of the preferred embodiments'of my invention, it is clearly understood that my invention is not limited to these details, but is capable of other adaptations and modifications within the scope of the appended claims.

What I'claim is new and desire to secure by Letters Patent of the United States is 1.;An apparatus for filling with liquid in thermostatic bulbed container having a stem extending thereinto, comprising a receptacle for the liquid in which the container is partly immersed to form a liquid seal, an exhausting tube extending from.

within the liquid in the receptacle through the stem to the upper end of the container,

refer to provide the tubes with and a source of suction communicating with the lower end of the tube for sucking the liquid up into the container.

2. An apparatus for filling the container of a liquidexpansion thermostat with a liquid comprising an open vessel for containing the liquid, an exhausting tube extending from the bottom wall of the vessel through the liquid therein for extending into the interior of the container to suck the liquida the uppermost portion of the interior of the container by way of the stem, anda source of suction communicating with the other end of the tube, for sucking the liquid up into the container through the stem.

4. The method of charging with a liquid 'thebulbed container of a fluid expansion thermostat having a stem extending thereinto forming a trap in the contalner, which consists in immersing the outer end of the stem in a body of the liquid with which the container is to be charged, sufliciently to form a liquid seal for the stem and evacuating the upper end of the container by an exhausting tube extending thereinto by way of the liquid sealed stem for sucking the liquid up into the container.

In witness whereof, I hereunto subscribe my name this 10th da of March, 1923.

JULI N G. GOODHUE. 

